Leaning vehicles having more than one front or rear wheels require a frame that is pivotally connected to the two-wheel suspension assembly to permit the vehicle to lean. One such vehicle is disclosed in U.S. Pat. No. 6,328,125 (Van Den Brink et al.), which describes a three-wheel vehicle having a frame pivotally connected to a two-wheel rear suspension assembly, and drive train structured in such a way that, the frame and the front wheel can lean into a corner while the two rear wheels remain substantially vertical.
In addition to having the frame lean into a corner while turning a leaning vehicle, the two front or rear wheels of the leaning vehicle may also tilt in the same direction as the frame to reflect the general behavior of a motorcycle. In order to allow the two front or rear wheels to lean to one side or the other, the suspension assembly must be connected to the wheels in such a manner that the suspension components do not interfere with the leaning wheels. An improvement of the vehicle disclosed in U.S. Pat. No. 6,328,125 in which the two rear wheels can lean into a corner is disclosed in U.S. Pat. No. 6,863,288 also to Van Den Brink et al.
US Pat Application No. 2005/0167174 A1 (FIG. 3) discloses a relatively complex front suspension and steering system for a leaning vehicle equipped with a pair of independent front upright suspensions mounted on an ‘articulated quadrilateral structure’ adapted to tilt the front wheels with the frame when negotiating a curve. The disclosed suspension is adapted to allow the front wheels to independently move up and down while simultaneously remaining parallel to each other and to the frame when the vehicle is leaning into a corner like a motorcycle. This suspension system is bulky and complex and it is specifically designed for two front wheels that are relatively close to one another. This type of suspension would be difficult to employ on a larger vehicle in which the wheels are farther apart.
Another well known type of front suspension assembly used in leaning vehicles in which the front wheels tilt into the corner is the double A-arm type front suspension. The double A-arm type suspension is adapted to transmit the leaning motion of the vehicle frame to the wheels by virtue of its substantially parallel upper and lower A-arms connected to upper and lower points of the wheels respectively. When the vehicle leans into a right corner for instance, the right upper A-arm pushes on the upper point of the right wheel while the right lower A-arm pulls on the lower point of the right wheel thereby tilting the right wheel towards the corner. At the same time, the left upper A-arm pulls on the upper point of the left wheel while the left lower A-arm pushes on the lower point of the left wheel thereby tilting the left wheel towards the right corner as well. One such vehicle is the Mercedes F300 Life Jet which was first unveiled at the 1997 Frankfurt Motor Show (Germany) but never reached production. This type of front suspension with the appropriate tilting connections allows the wheels and frame to lean, however the angle to which the wheels can lean and thus the angle to which the vehicle frame can lean is limited. Furthermore, the left and right spring and shock absorber assemblies are directly involved in the leaning of the vehicle such that the suspension becomes less effective when the vehicle is leaning. Also, the displacements of multiple A-arms implies that the front of the vehicle must remain substantially free of other components to avoid interferences.
Thus, there exists a need for a leaning vehicle having a two-wheel front suspension assembly that permits tilting of the wheels to a greater degree than that of the prior art leaning vehicles and that remains effective when the vehicle is leaning into a corner.